Bristles, method and device for production thereof and brushes

ABSTRACT

The invention concerns a bristle for a brush, in particular a cleaning brush, a toothbrush or an application brush, wherein the bristle has a lower root region with which it can be mounted in or to a bristle support or which forms part of the bristle support, and a free length disposed outside of the bristle support above the root region which is composed of a shaft region bordering the root region and a flexing region disposed thereabove, wherein the shaft region is composed of a lower shaft base section bordering the root region and a shaft section disposed thereabove, and wherein the flexing region is composed of a lower active and flexing section bordering the shaft region and a tip section which is disposed thereabove and forms the free end of the bristle, wherein the bristle has a continuous depression-free jacket in the shaft base section and, at least in sections of the jacket in the flexing region, a profiling which is formed by elevations and/or depressions and which lies in an outer surface of the bristle.

This application is the national stage of PCT/EP03/02795 filed on Mar.18, 2003 and also claims Paris Convention priority of DE 102 12 701.8filed Mar. 21, 2002.

BACKGROUND OF THE INVENTION

The invention concerns a bristle for a brush, in particular a cleaningbrush, toothbrush or application brush and a method for producing acorresponding bristle of thermoplastic polymers through casting,preferably injection molding. The invention also concerns a device forcarrying out the method and a brush comprising corresponding bristles.

Animal hair and natural fibers which were previously used as bristlematerial for producing brushes, paint brushes or the like have beensubstantially replaced by plastic bristles, wherein the production ofthe bristle material is based largely on the well established productionof synthetic textile fibers, i.e. extrusion or spinning processes.However, a bristle is subjected to completely different conditions thanan endless fiber in a fiber composite. It is free and fixed at only oneend and can be regarded in terms of stability as a freely projecting barwhich bends and which is fixed at one end. Pressure or compressionforces and sometimes also tensile forces occur during use. Compared toendless fibers, the stability requirements are different with regard tobending strength, fatigue strength under reversed bending stresses,buckling resistance and bend recovery.

Corresponding bristles can be used for toothbrushes, cleaning brushes orbrooms in particular in the field of hygiene, applicators for powdery orliquid media, in particular liquids, cleaning agents, solvents, paintsand varnishes and cosmetics, for application pads, cleaning padsincluding mats for cleaning shoes, combs, hairbrushes pr technicalbrushes. By way of example, bristles for a toothbrush are describedbelow. The invention is however not limited thereto.

As has been known for a long time, the cleaning effect of a toothbrushcan be improved by providing a structure or profile on the outer surfaceof the bristle. If the bristles are e.g. provided on their outside withwart-like nubs (DE 100 17 167.2) or ribs (U.S. Pat. No. 1,773,969) theplaque removing effect on the tooth can be increased by up to 50%.

Such bristles having a structure or profile on their outer side areusually produced in the desired cross-sectional shape by extrusion orare surface-formed under continuous processing following production asan unprofiled monofilament. Profiling improves the brushing and cleaningeffect but has the disadvantage that the profiling impairs the stabilityproperties of the bristle in its mounting region and the bristle tendsto bend or kink.

The known externally profiled bristles also have negative effects onhygiene. Due to the profiling, chambers and undercuts are formed on thebristle proximate to and, in particular, in its fixing region in whichimpurities may deposit which cannot be removed or which can only beremoved to an inappropriate degree due to the densely packed bristlefield. This can produce fungal, bacterial and microbial growth.

To increase the brushing and cleaning effect of a bristle, U.S. Pat. No.3,256,545 and U.S. Pat. No. 4,167,794 suggest providing a widened headat the free end of the bristle, which protrudes laterally by an amountcorresponding to several times the diameter of the cylindrical bristlestem. In this design, the fixing region is loaded with high bendingmoments due to the mass and the brushing resistance of the head, whichmay cause the bristle to kink even after a short time of use therebyrendering the bristle unusable.

It is the underlying purpose of the present invention to produce abristle of the above-mentioned type which is hygienically impeccable,strong, efficient and highly stable for a long period of time. Theinvention should moreover produce a brush comprising correspondingbristles and propose a method for producing a corresponding bristlethrough casting and in particular injection molding whose bendingbehavior and bend recovery exceed that of extruded bristles, whilepermitting optimum realization of the theoretical elasticity values andtensile strengths and which permits production of bristles of highquality over large length ranges even with relatively smallcross-sections to be able to produce bristle geometries and bristlearrangements in a simple fashion while thereby adjusting the brushes andpaint brushes to the requirements of the final product. The invention ismoreover based on providing a device, which is suitable for carrying outthe method.

SUMMARY OF THE INVENTION

With regard to bristles, this object is achieved through a bristlecomprising the features of the independent claim.

The inventive bristle has no profile in and close to its lower fixingregion to obtain good bristle rigidity and stability properties and toavoid formation of recesses and undercuts to reliably eliminate thehygiene problems associated therewith. In particular, the bristle canthereby be designed according to the static requirements, i.e. withrespect to a desired deformation behavior and bend recovery. To renderthe bristle highly efficient (i.e. high brushing and cleaning effect),the surface of its free length is profiled at least in sections at aseparation from the fixing region.

To explain the invention, the individual sections of a bristle will beinitially defined below with reference to FIG. 1. FIG. 1 shows a bristle100 having a lower substantially truncated root region a which servesfor connecting to or into a bristle support or bristle body or which ispart of the bristle support itself. Above the root region, the bristle100 comprises a protruding free length l which projects past the bristlesupport after mounting the bristle. The free length l of the bristle 100is divided into two main regions, a shaft region S and a flexing regionF, each of which are subdivided into two sections. The shaft region Sdirectly borders the root region a. It can comprise e.g. 15% to 85% andin particular 35% to 65% of the free length l of the bristle 100. Theflexing region F joins above the shaft region S and occupies the rest ofthe free length l. The shaft region S is composed of a lower shaft basesection b bordering the root region a and a shaft section c disposedthereabove. The shaft base section b can assume e.g. 10% to 40% of thelength of the shaft region S or even be relatively short, i.e. have anaxial length of≦10 mm and in particular≦1 mm. The flexing region Fdisposed above the shaft region S, which is decisive for the brushingand cleaning properties of the brush, is composed of a lower active andflexing section d bordering the shaft region S and a tip section tdisposed thereabove forming the free end of the bristle 100. The flexingand active section d can assume e.g. 50% to 95% of the length of theflexing region F.

To prevent collection of impurities close to the fixing or mountingregion of the bristle, the invention provides that the bristle has acontinuous depression-free jacket at least in the shaft base section b.The cross-section of the bristle in the shaft base section b can therebybe circular, oval or even polygonal with rounded corners. The jacketsurface is preferably smooth and without fractures or undercuts.

In the flexing region F, i.e. the active and flexing section d and/orthe tip section t, at least sections of the jacket of the bristle have aprofiling formed through elevations and/or depressions within anenveloping surface of the bristle which increases the brushing andcleaning effect of the bristle.

The profiling may also be formed in the shaft section c and inparticular in its upper section joining the active and flexing sectiond. In a preferred embodiment of the invention, the cross-section of thebristle also has a continuous and depression-free jacket in the shaftsection c as in the shaft base section b. It is thereby not necessarythat the shaft section c and the shaft base section b have the samecross-sectional shape or cross-sectional dimensions.

To ensure stability of the bristle for a maximum service life, theinvention may provide that the cross-sectional dimensions of the bristlethroughout the region of its free length l, i.e. in the shaft region Sand in the flexing region F do not exceed the cross-sectional dimensionsin the region of the shaft base section b, and in particular of itslower cross-section at which the shaft base section b joins the rootregion a.

Due to the continuous depression-free jacket provided in the shaft basesection b and the profiling formed in the flexing region F, the bristlehas regions of different cross-sectional shape. The cross-sectionalshape of the bristle in the longitudinal direction can thereby changeonce or several times. The bristle may consist e.g. of sequentialregions with round, oval, polygonal (in particular square, triangular,rectangular or octagonal), Y-shaped, crossed or star-shaped, annular oralso arc-shaped or circle segment-shaped cross-section.

In a variant, at least sections of the outer envelope of the bristle inthe region of its free length l, may have the shape of a surface of astraight cylinder and/or of a cone or truncated cone. In particular, thefree length l of the bristle can be formed from a sequence of regions ofdifferent geometrical shape. The regions may be e.g. cylindrical,conical, constricted (hyperboloidal) or bulged (shape of a barrel body).The transitions between the regions of differing cross-sections and/ordiffering geometrical shapes and the transitions between the profilingsand/or between the profiling and the depression-free jacket should besmooth and as continuous as possible.

If the bristle is conical along its entire free length or at least insections, the conicity angle should be less than 5° and in particularless than 1°. The enveloping surface diameter of the bristle can bebetween 0.010 mm and 10.0 mm, wherein bristles having an envelopingsurface diameter of≦1.0 mm are preferred. The degree of hardness of thebristle can be determined through corresponding selection of thediameter and/or the cross-sectional shape and/or the composition of thebristle from a succession of different geometrical sections and/orthrough material selection.

In a preferred embodiment of the invention, the profiling is formed inthe upper region of the active and flexing section d and/or in the tipsection. In this connection, one single profiling may be provided.Alternatively, several similar or different profilings can be adjacentto another in the longitudinal direction of the bristle. In particular,a region with a preferably smooth, depression-free surface can bedisposed between two axially separated profilings.

The surface envelope may be smooth or, in a further development of theinvention, at least sections of that outer surface of the bristle mayhave a roughness, in particular, in the micro-range.

The profiling can be designed in various ways. In a first embodiment,the profiling comprises a groove extending around the bristle such asone single groove, which helically surrounds the bristle. It is alsopossible that the groove extends annularly around the bristle,substantially perpendicular to the longitudinal extension of thebristle. In this case, several grooves should be disposed, one above theother, wherein a peripheral edge, preferably sharply structured, isformed between neighboring grooves to increase the cleaning effect. Thecross-section of the groove can be concavely rounded or V-shaped.

Alternatively or additionally, the profiling can comprise severalelongated grooves extending in the longitudinal direction of thebristle, wherein the longitudinal grooves are preferably distributedabout the circumference of the bristle and are preferably disposed nextto each other. A sharp edge may also be formed between neighboringgrooves in this embodiment.

The profiling may also be generated when the bristle has, in the regionof the profiling, a crossed or star-shaped cross-section with severalribs which extend in the longitudinal direction of the bristle and whichare distributed about the bristle circumference. The ribs may have asharp outside edge or be rounded.

In a further embodiment, the bristle has a polygonal, in particulartriangular or rectangular cross-section in the region of the profilingwherein the cross-sectional edges may be sharp or rounded.

It is also possible that two of the above-mentioned profiling types aresuperposed on the bristle. For example, a bristle having ribs extendingin the longitudinal direction can also comprise longitudinal and/ortransverse grooves, in particular, on the outer sides of the ribs.

In a particular embodiment of the bristle, preferably for use in anapplication brush, only the tip section t may be provided with aprofiling. The geometrical cross-sectional shape of the bristle maythereby change in the tip section. Alternatively, the tip section t maybe formed by axially extending fingers or comprise at least one axialprofile element which projects in an axial direction of the bristle pastthe underlying active and flexing section d and to thereby form the tipsection t.

In a further development of the invention, the bristle is composed ofaxially sequential sections or parts, which consist of differentmaterials. The materials may thereby have different properties. Inparticular, the shaft base section b and optionally also the shaftsection c may consist of a material which provides the bristle with thedesired stability and rigidity while the active and flexing section dand the tip section t may be made from a material which is particularlywell suited for achieving good brushing and cleaning effect and possiblyalso for accommodating additives in the bristle, e.g. substances foranti-microbial action. The bristle material may also be reinforced, atleast in sections. This can be effected either through addingreinforcing fibers or reinforcing fiber mixtures and/or formation of abristle core from a stable, hardening material.

The axially sequential sections or parts of the bristle, which consistof different materials, can have different colors to mark theirproperties. At least one of the parts may provide an indication of wear.

The free end of the bristle, i.e. the outer region of the tip section tis preferably deburred or rounded and the bristles may have a slightsurface structure through addition of non-melting particles during theproduction process, in particular during the casting or injectionmolding process. The non-melting particles impair the transversecontraction during the slight shrinkage of the cooling bristles andtherefore produce a slight wavy surface structure.

Moreover, at least sections of the bristle may be provided with acoating that is preferably disposed in the region of the structure andbears e.g. the additives and/or substances for antimicrobial action. Thecoating may provide an indication of wear.

The deformation properties of the bristle can be influenced by an innerhollow axial channel which starts from the root region a and which maysupply the substances for antimicrobial action during use of thebristle. The hollow axial channel can extend through a partial region ofthe bristle or through approximately the entire bristle up to shortlybelow the free end. In a further development of the invention, thehollow channel extends through the entire bristle and opens into the tipregion, i.e. is open at the tip of the bristle.

The bristle may be formed as a symmetrical body with the transitionbetween the profiling and the unprofiled jacket being in a plane, whichextends substantially perpendicular to the longitudinal axis of thebristle. A bristle of this type can be used in any direction, since itsproperties are the same at all angular orientations. To provide thebristle with a preferred effect in a certain radial direction and, inparticular, a brushing and cleaning effect, a further development of theinvention configures the transition between the profiling and theunprofiled jacket to be located in a plane which extends at an anglewith respect to the longitudinal axis of the bristle. The plane ispreferably within an angular range of between 30° and 60° relative tothe longitudinal axis of the bristle.

To influence the stability and strength properties and, in particular,the deformation behavior of the bristle, the root region a and inparticular the shaft base section b may have a jacket. The jacketmoreover reliably prevents introduction of impurities. Alternatively,the entire bristle may be provided with a jacket. The jacket may therebybe part of the bristle support.

The bristles may be made from thermoplastic materials, elastomers,thermoplastic elastomers, duroplastes, silicons or other materials,which can be cast, injection-molded or compressed. Two materials maythereby border one another within a cross-section of the bristle andthereby form a multi-layer bristle (side-by-side construction).

After production, the bristles may be finished on at least part of theirlength in a mechanical, thermal or chemical fashion through e.g.coating, coloring, varnishing, vapor-deposition or galvanization. Thebristle may also be polished, ground or roughened. The free end of thebristle can be rounded, sharpened or split. Surface finishing of thebristle may include sandblasting or exposure to laser beams to therebyprovide a surface structure. Finishing may also effect a color change ofthe bristle, at least in sections, to visualize e.g. usage or wearconditions or effects.

Finishing may include chemical structuring or etching. If finishing isprovided only on part of the bristles in particular the bristle ends, awear indication may be provided as is particularly useful fortoothbrushes and hygiene brushes.

An inventive bristle can be produced e.g. through casting, materialremoval, compression molding or compression. In a preferred embodimentof the invention, the bristle is produced through injection molding inparticular of a thermoplastic polymer. A method may be thereby used asdisclosed in WO 02/03831, the complete disclosure of which is herebyincorporated by reference.

Departing from the known injection molding method, wherein the moltenpolymer mass is injected under pressure into a bristle-molding channelof predetermined length and predetermined cross-sectional shape alongthis length, and the channel is vented during injection molding, thisobject is achieved in that the magnitude of the injection pressure isadjusted in dependence on the cross-sectional shape of thebristle-molding channel such that a shear flow of the molten polymermass is generated with high core speed in the center of the moltenpolymer mass flow and large shearing effect due to wall friction underdistinct longitudinal orientation of the polymer molecules, at least inthe region of the molten polymer mass close to the wall, which ismaintained along the channel, wherein the channel is simultaneouslyvented along its length to support maintenance of the shear flow.

This is based on the realization that the bending behavior of amonofilament can be primarily increased through generation andmaintenance of a molecular orientation which has previously not beenrealized in injection molding of bristles, brushes and paint brushes.The molecular structure in a molten polymer mass flow can only besubstantially influenced using sufficiently narrow cross-sections andmelt flow forced to a speed profile having strong shearing effects todeform and stretch the energetically most favorable tension-free balledstructure. For this reason, in accordance with the invention, theinjection pressure is set to a sufficiently high level that a steep flowprofile forms in the bristle-molding channels which is characterized bya high core speed in the center of the flow and large shearing effect inits edge region due to the wall friction of the molten polymer mass onthe channel wall, wherein the shearing forces due to wall friction arelarger the higher the speed difference between neighboring flow layers.A flow profile of this type with high core speed moreover ensuresperfect filling of the mold of the bristle-molding channel even for thenarrowest of cross-sections (small bristle diameter) and large channellength (bristle length).

The speed profile can be set in dependence on the predeterminedcross-sectional shape along the length of the bristle-molding channelthrough a correspondingly high, optionally variable injection pressure.The polymer molecules are thereby oriented longitudinally close to thechannel wall and, to a reduced degree, within the entire melt flow,wherein the magnitude of the core speed moreover prevents prematuresolidification of the molten mass, even for small cross-sections andlarge lengths. High pressure alone is not sufficient for rapid fillingof a narrow molding channel. In accordance with the invention, thechannel is vented along its length such that the shear flow with highflow speed is maintained up to the end of the channel and the desiredlongitudinal orientation of the molecules reaches the bristle tip.

Practical tests have shown that the injection pressure should be atleast 500 bar (0.5·10⁵ kPa) and is a function of the cross-sectionaldependence of the bristle-molding channel. For the quality bristlesunder discussion having an average bristle diameter of e.g. 0.3(measured at half the length) and a corresponding cross-section of thebristle-molding channel and with a length of 10.5 mm, the desired speedprofile can be produced with an injection pressure of at least 500(0.5·10⁵ kPa). Approximately ⅔ of the above-mentioned injection pressurecan usually be converted into specific pressure in the bristle-moldingchannel such that the molten polymer mass in the channel should have apressure>300 bar (0.3·10⁵ kPa).

During solidification below the crystal melt temperature, thermoplasticmaterials form crystallites, which influence the modulus of elasticity(E module) and the tensile strength (tearing strength) in dependence ontheir shape and configuration. The formation of needle crystals has apositive influence on stiffness through increase of the E modulus andstrength due to an increase of the tensile strength and initiallyrequires linked elongated crystal seed formation on parallel molecularsections. This seed formation can be amplified compared to isothermalcrystallization through the introduction of forces as given i.a. in flowprocesses. The inventive high injection pressure and the high flowvelocity of the molten polymer mass in the bristle-molding channelobtained thereby therefore not only promote longitudinal molecularorientation but also crystal formation, wherein the high pressuresimultaneously increases the packed density of the crystals throughincreased loading. The partial crystallization of the molecularlyoriented molten mass increases the relaxation time, i.e. the molecularorientation lasts for a longer period.

The above-described effects are further supported in a supplement to theinvention in which the bristle-molding channel is cooled.

The narrower the cross-section and the larger the length of thebristle-molding channel, the more reasonable it is to keep the channelwalls warm to maintain the viscosity of the molten polymer mass andobtain complete filling of the mold. When setting the inventive methodparameters, the filling of the mold is also guaranteed when thebristle-molding channel is cooled. Cooling of the channel and associatedintroduction of forces additionally promote formation of crystals andincrease relaxation time. The stabilizing outer layer of the bristle,which is produced on the channel wall, permits increase of thepost-pressure, which is common in injection molding. The higher thepost-pressure, the stronger the crystal seed formation in the stillmolten bristle core. The pressure simultaneously increases the meltingtemperature and enhances cooling of the molten mass for a given masstemperature, thereby further producing a positive effect on the crystalgrowth speed and impeding relaxation of the molecules.

The high injection pressure and high flow velocity require particular oradditional measures for rapid and effective venting to ensure completemold filling and to prevent cavities in the molding channel or airinclusions in the molten mass. In the conventional injection moldingmethods, the bristle-molding channel is vented when the cavity iscompletely closed at the end of the channel or, for a longitudinallysplit injection mold defining the channel, in two planes parallel to thebristles. In the first case, for forming a perfect, preferably roundedbristle end, the venting must be drastically reduced to prevent moltenpolymer mass from getting into the venting regions. For venting parallelto the bristles, the mold-separating plane lies in the flow directionwith the consequence that the molten polymer mass penetrates into eventhe most narrow of venting gaps and produces mold-separating seams alongthe bristle jacket.

The invention therefore proposes venting of the bristle-molding channeltransverse to the flow direction of the molten polymer mass, wherein theventing is preferably effected in several planes transverse to the flowdirection of the molten polymer mass. The number of venting planes ishigher, the longer the bristle-molding channel such that, forpredetermined channel length, the venting is controlled in dependence onthe speed of the molten mass front. Since venting is possible in such aplane about the entire periphery of the bristle channel, there is acorresponding gap length transverse to the flow direction which islarger than that of a bristle-parallel mold-separating plane and whichcan be implemented over a plurality of planes.

The venting planes can be provided at equal separations along the lengthof the bristle-molding channel in dependence on the volume to be vented,optionally with progressive or degressive separation in the flowdirection of the molten polymer mass. This permits simultaneousmaintenance of a sufficiently high counter pressure in the channel toobtain uniform filling of the mold.

The bristle-molding channel can be vented merely through displacement ofair through the flow pressure of the molten polymer mass. However,venting can also be supported by external under-pressure.

The inventive method permits injection of the molten polymer mass into abristle-molding channel from the injection side with a cross-section,which is substantially uniform to produce a substantially cylindricalbristle, which could not be produced with previous injection moldingtechnology for bristles and brushes.

The cross-section may substantially continuously taper from theinjection side to produce a bristle with preferably only weak conicity,which is desired for many applications to increase the bendingelasticity from the bristle root to the bristle end. Such conicitypromotes maintenance or even reinforces a steep velocity profile withhigh core speed and shearing effect in the edge region which increasesalong the length such that, despite increased flow resistance, themolecular orientation and crystal formation is enhanced towards thebristle end.

Injection molding produces precisely sized bristles with a tolerance of±3% in cross-section and in length while extruded bristles with the sameconstructive parameters have tolerances of ±10%. The initially circularcross-section of extruded bristles is ovalized through processing whichis unnecessary for the bristles produced according to the presentinvention.

Injection molding technology usually regards mold removal slopes of afew degrees (>1.00°) as necessary to be able to properly remove theinjection-molded part. Ejectors usually support mold removal. When thebristles are injection-molded in accordance with the above-mentionedprior art, the mold slope must be considerably larger to prevent tearingoff of the bristle during removal from the mold (U.S. Pat. No.3,256,545). This is one reason why prior art uses injection-moldingtools, which have a bristle-parallel mold-separating plane, therebyaccepting the above-described disadvantages. The inventive methodpermits reduction of the mold slope to a value of 0° with sufficientmold filling. Slender bristles of great length can be produced withrelatively small conicity in the region of 0.2 to 0.50 when the positiveproperties of a conical bristle are desired having a bending angle,which increases towards the bristle end. Mold removal is simplified bycrystal formation promoted by the longitudinal orientation and theassociated increase in the tensile strength (tear resistance) of thebristle, in particular in the region close to the wall, which isimportant for removal from the mold. Further measures for facilitatingremoval from the mold are described in connection with the device.

In a further embodiment of the inventive method, the molten polymer massis injected into an inlet region which narrows like a nozzle towards thebristle-molding channel for generating an extension flow to produce abristle with a widened root region which optionally tapers continuouslytowards the actual bristle.

Such narrowing generates an extension flow, which produces considerablemolecular orientation and, due to flow properties, correspondingboosting of the flow profile after the narrowing. The narrowing istherefore preferably disposed close to the injection side. It is alsopossible to provide narrowings along the length of the bristle-moldingchannel to obtain stepped bristles wherein, in this case as well, thenarrowings have positive effects on the molecular structure and crystalformation.

After an optional upstream inlet region, the cross-section of thebristle-molding channel is preferably selected with a maximum width of≦3 mm such that the injection-molded bristle has a correspondingdiameter with an optionally broader root region. Bristles having thiscross-section and broader root region cannot be produced throughextrusion or spinning. The term “largest width” in this connection meansthat the bristle may also have a cross-section, which differs from acircular shape, e.g. oval, wherein the largest width of the lengthcorresponds to the larger axis of the oval.

In applications of the inventive method, the ratio between the largestwidth and the length of the channel may be selected to be ≦1:5 to1:1000, preferably up to ≦1:250. Bristles can e.g. be produced whichhave a length of between 15 mm and 750 mm with a maximum diameter of 3mm in or close to the root region. The smaller the largest width, theshorter the length. For stringent requirements, e.g. for toothbrushes,application brushes etc. diameters above the root region of ≦0.5 mm arerecommended which permit bristle lengths of more than 60 mm in theinventive method.

The inventive method can be modified in a likewise advantageous fashionwhen the molten polymer mass is injected simultaneously into severalneighboring bristle-molding channels thereby forming a correspondingnumber of bristles such that a set of bristles can be produced in oneinjection process. Minimizing of the separation of the bristle-moldingchannels produces bristle arrangements in the form of pucks throughslight compacting of the removed bristles.

The number and arrangement of the bristle-molding channels can beselected such that the entire bristle stock of a brush or of a paintbrush is produced in one injection process, wherein the separationsbetween the bristles and their geometrical relationships can be variedin accordance with the desired arrangement in the bristle stock.

A further embodiment provides that the molten polymer mass is injectedinto the neighboring bristle-molding channels thereby simultaneouslyforming a connection between at least two bristles, wherein theconnection may serve for further handling of the connected bristles andalso as an aid for connection to a brush body, paint brush handle or thelike. Alternatively, after injection of the bristles from a polymer, amolten polymer mass of another polymer can be subsequently injected toproduce a connection between the bristles. The connection may be in theform of bars, grids connecting several bristles, or the like. The use ofdifferent polymers with a joining factor of ≧20% guarantees sufficientlysecure connection.

The connection may further be designed such that it forms a bristlesupport which may simultaneously constitute the brush body or partthereof or which can be completed into a brush body or paint brushhandle by injecting at least one further molten polymer mass which maycomprise a different thermoplastic or thermo elastic polymer.

In a further variant of the method, several bristles can be injectedwith different lengths such that, in combination with the bristlesupport connecting them, a complete bristle stock or partial stock canbe produced for a brush or a paint brush, wherein the bristle ends areat different heights along a flat or non-planar envelope surface so thatthe finished brush has optimized bristle end contours.

The bristle group can also be injected with different cross-sections topermit different effects in predetermined regions of a finished brush.

Likewise, the bristle group can be injected with a cross-sectionalshape, which differs along its length. The bristle group can also beinjected in a mutually non-parallel fashion to produce a bristle stockwith differing bristle orientations.

In accordance with another embodiment of the method, bristles having thesame geometry but different bending elasticity (hardness) can begenerated through injection molding of different molten polymer massesin the same molding channels. For extruded bristles for brushes havingdifferent degrees of hardness (textures) e.g. for toothbrushes havinghardness gradations of soft, medium, hard, the desired degree ofhardness could be influenced only via the diameter of the bristle, i.e.toothbrushes of the same structure had to prepare and process up tothree different bristle diameters. The inventive method realizes thesedegrees of hardness merely through selection of the polymer andoptionally by adjustment of the injection pressure but with identicalbristle diameters.

Bristles can also be injected from a polymer or a polymer mixture, whichhave reduced secondary binding forces in the solidified state. Thesebristles can be cleaved after production through mechanical forcesthereby forming flags, if necessary only after further processing intobrushes or paintbrushes.

The bristles can be injected from a polymer comprising additives, whichbecome active during use. The additives may have mechanical, e.g.abrasive effect or, e.g. for toothbrush bristles, be additives withprotective, therapeutical or remineralizing action. Numerous additivesof this type are known.

The invention also concerns a device for injection-molding bristles fromthermoplastic polymers, comprising a means for producing the injectionpressure and an injection mold which has at least one supply channel forthe molten polymer mass and at least one cavity in the form of a moldingchannel with a mold contour which corresponds to the length andcross-sectional shape of the bristle to be produced, wherein the moldingchannel has associated venting means for releasing the air displacedduring injection molding. Devices of this kind are known from theabove-described prior art.

A device of this type is characterized, in accordance with theinvention, by means for generating an injection pressure of preferablyat least 500 bar (0.5·10⁵ kPa) and the venting means have ventingcross-sections which are distributed along the length of the moldingchannel and which are designed to form, in cooperation with theinjection pressure, a shear flow with high core speed in the center ofthe molten polymer mass and large shearing effect on the wall of themolding channel.

Such a device can produce bristles through injection molding asdescribed in connection with the method. Compared to known injectionmolding devices for producing bristles or one-piece brushes withbristles, the device according to the invention is designed such thatthe desired flow dynamics is obtained in the channel forming thebristle.

The means for generating the injection pressure is preferably designedsuch that injection pressures of between 500 and 4000 bar (0.5·10⁵ to4·10⁵ kPa) can be set depending on the length and cross-sectional shapeof the molding channel. The pressure is higher, the smaller thecross-section of the bristle to be produced and the greater its length.

The means for generating the injection pressure and ventingcross-sections on the molding channel are designed with respect toconstruction and control such that the molten polymer mass in themolding channel has a specific pressure of at least 300 bar (0.3·10⁵kPa) to 1300 bar (1.3·10⁵ kPa). This design is adjusted to the mass flowand flow resistances to be overcome upstream of the molding channel.

If the injection pressure on the generating means is sufficiently high,the injection pressure can advantageously be controlled depending on thelength and the cross-sectional shape of the molding channel to permitinjection of injection molds of different geometrical shapes with oneinjection-molding unit.

This purpose is supported in that the venting means have ventingcross-sections, which can be controlled depending on the specificpressure.

In the inventive device, the injection mold is advantageously associatedwith coolant, which may be external cooling after each injection moldingcycle or after removal from the mold. The molding channel in theinjection mold may have associated cooling means for keeping the moldingchannel at a reduced temperature.

In a particularly preferred embodiment of the invention, the injectionmold consists of several molding plates disposed in layers transverse tothe longitudinal extension of the molding channel, each of which definesa longitudinal section of the molding channel.

In contrast to prior art with more or less block-shaped injection molds,the invention provides a structure of stacked molding plates. Thisstructure permits forming of minimum bore cross-sections with highprecision in each molding plate of low thickness. This and any otherproduction technology would fail for larger bore depths. This is also areason why longitudinally separated injection molds were necessary forthe production of narrow cross-sections. Their disadvantages aredescribed in connection with prior art. The inventive decomposition ofthe injection mold into several plates permits realization of moldingchannels of large length with high and reproducible precision over theentire length. The molding plates which comprise the end of the moldingchannels and form the bristle end can have, due to the small thicknessof the molding plates, cavities with only small depth to form a bristleend having clear contours, without any mold separating seam, and withoutadditional venting means. Oxidation of the polymer, which can beobserved in narrow mold cross-sections through the so-called dieseleffect, does not occur due to the small depth of the cavity.

The layered structure of the injection mold moreover permits formationof the venting means on the molding plates, i.e. with a frequencycorresponding to their number. The venting means are preferably formedbetween the mutually facing support surfaces of the molding plates e.g.through narrow gaps or channels. The high flow velocity of the moltenpolymer mass perpendicular to such narrow gaps or channels prevents themolten mass from penetrating into the venting openings, despite the highpressure. The venting openings may therefore be larger than in atwo-shell mold whose mold-separating plane is in the flow direction ofthe molten mass. The venting cross-sections may be formed with a maximumwidth of only a few μm up to 300 μm.

The venting means are preferably formed completely or partially throughsurface roughness on the mutually facing surfaces of the molding plates.

In a further advantageous embodiment, the venting means have ventingcross-sections which increase outwardly from the surface of the moldingchannel such that the air can freely escape after passage of thenarrowest point of the venting cross-sections.

The displacement of air caused by the specific pressure in the moldingchannel can be supported when the venting means is connected to anexternal under-pressure source.

The device may be designed such that the molding channel has across-section which is substantially constant along its length or whichsubstantially uniformly tapers towards its end to produce cylindrical orslightly conical bristles.

Practical injection tests under the stated method conditions have shownthat the molding channel can taper at an angle <1.0°, with linear axis,to produce sufficient mold slope for removing a slightly conicalbristle, having excellent bending behavior, from the mold.

The molding channel can have a cross-section, which discontinuouslytapers towards the end to produce specially designed bristle ends asrequired by the application for the finished brush.

The largest width of the cross-section of the molding channel ispreferably ≦3 mm. This covers the bristle cross-sections desired forquality brushes and paintbrushes.

At least one molding plate can be disposed on the injection side havinga widening which tapers towards the molding channel and can be connectedupstream of the molding plates defining the molding channel having theabove-mentioned largest width at their sides facing the supply channelto reinforce the cross-section on the bristle root and on the bristlebase and also to obtain, due to this widening, an extensional flow atthe inlet region of the molding channel to support formation of thedesired flow dynamics. The widening can narrow like a trumpet towardsthe molding channel to produce a smoothly connecting shoulder at thebristle and to the support connecting the bristles, brush body or thelike. This is particularly important for hygiene brushes of any type.

The ratio between the largest width of the cross-section of the moldingchannel and its length is preferably between 1:5 and 1:250 but may alsobe 1:1000 wherein the ratio is closer to the higher value the narrowerthe cross-section of the molding channel and closer to the lower valuethe larger the narrowest cross-section.

A further embodiment of the invention provides that the number andthickness of the molding plates is matched to the length of the moldingchannel, wherein the number of the molding plates is inverselyproportional to the ratio between the largest inner diameter of thecross-section and the length of the molding channel. The number ofmolding plates, which belong to an injection mold, can be variable to beable to produce bristles of varying length with the same mold.

The molding plates preferably have a thickness, which is approximatelythree to fifteen times the central diameter of the molding channel. Fora bristle of an average diameter of 0.3 mm and a length of 10.5 mm, themolding plates have e.g. a thickness of 1.5 mm to 2.00 mm. Alongitudinal section of the molding channel of 1.5 mm to 2.0 mm can bedrilled with high precision into the molding plate.

The molding plates are movable perpendicular to their plate plane,individually or in groups. This permits, in particular, removal of thebristle from the mold in a non-conventional fashion, wherein e.g. themolding plates, starting with the molding plate having the mold contourat the end of the molding channel and ending with the molding platefacing the supply channel, can be subsequently removed eitherindividually or in groups.

The molding plates are reliably kept together under the method-specifichigh closing pressure of the injection-molding machine and are notsubjected to any deforming forces, despite their low thickness.Moreover, the venting openings are kept closed by the closing pressureand, unlike channels with longitudinal venting, require no additionalmeans to keep them closed.

Practical tests have shown that the inventive narrow cross-sections andchannel lengths require considerable extraction forces to release thebristles if e.g. only two molding plates are present. The bristleusually breaks. Increasing the number of plates and their successiveseparation from each other permits damage-free removal of the bristlefrom the mold, in particular when the molding plate facing the supplychannel is removed last. During removal from the mold, the edges of theholes of each molding plate function as drawing nozzles to flatten any“polymer skin” formed in the mold-separating plane withoutdisadvantageously affecting the bristle jacket. In any event, thebristle ends are perfectly formed.

Individual molding plates may be displaceable parallel to theneighboring molding plates to exert transverse loading on the bristleafter injection molding, thereby optimizing the molecular structure.

In a further preferred embodiment, the injection mold has moldingchannels of different length and/or different cross-sectional shape toobtain e.g. a bristle stock of the desired geometry and configuration inone injection molding cycle.

In accordance with a further embodiment, the injection mold has moldingchannels comprising a central axis which extends at an inclined anglerelative to the direction of motion of the molding plates, wherein eachmolding plate comprises a longitudinal section of the molding channelwith a length which permits removal from the mold through successiveremoval of the individual molding plates, despite the angle variation.

The subdivision of the injection mold into a plurality of molding platesextending transverse to the molding channel permits subdivision of themolding channel into longitudinal sections which nevertheless permitremoval of the individual longitudinal sections from the mold withoutexcessive strain on the bristle or deformation thereof even when thebristle axis is inclined relative to the direction of motion of themolding plates (removing direction). In this fashion, bristle groups canbe produced in one single injection mold, wherein the bristles extendparallel to each other but at an angle relative to a bristle supportconnecting them or which have different angle orientations relative toeach other.

In accordance with a further embodiment, the injection mold has moldingchannels with a central axis which is curved relative to the directionof motion of the molding plates, wherein each molding plate defines alongitudinal section of the molding channel which is dimensioned suchthat removal form the mold is possible through successive lifting ofindividual molding plates in dependence on the curvature.

Wavy bristles can thereby be produced which can also be easily removedfrom the mold. It is also possible to simultaneously produce straight,wavy and curved bristles in one single injection mold.

In a further embodiment, the injection mold has at least one moldingplate which can be displaced in its plane relative to the neighboringmolding plates after injection-molding of the bristles to form, togetherwith these, a clamping means for all the bristles which acts on thecorresponding portion of the length of the molding channel.

The invention thereby permits use of parts of the injection mold tograsp the injected bristles and fix them in the injection mold along aportion of their length e.g. to separate the molding plates close to theends, in the removal direction, from the remaining molding plates and tocarry along the bristle blanks such that the bristles are exposed alonga middle partial length, i.e. between these molding plates and theremaining molding plates. Subsequent displacement of the clampingmolding plates and return of the molding plates close to the end in thedirection towards the injection end of the bristles, causes these endsto project past the molding plate at the injection side. Throughtransfer of the injection mold, optionally under further clamping by theholder, the injection mold can be connected to another injection moldingtool, which has a mold cavity forming a bristle support or brush body.In a further injection molding process, the projecting ends aresurrounded by a further molten polymer mass, which fills this moldcavity.

The clamping means may also serve as a transport holder to transfer theclamped bristles, after removal from the other molding plates, intoanother work station for connection to a brush body. This is alsopossible when the bristles are already joined via a connection such ase.g. bridges, grids or bristle supports. The clamping molding plate isthen located close to the transition between bristles and bristlesupport and the holder is removed in the removal direction along withthe connection and subsequently transferred, wherein the molding plateswhich serve as holders are replaced by an equivalent set of moldingplates to again obtain a complete injection mold. The holder can be aportable holder moving in a circulating path and be reused aftercomplete removal of the bristles from the holder to complement theinjection mold. If the connection is not directly required for thesubsequent fabrication steps, e.g. insertion, gluing, welding, injectingetc. it can also be removed and only the bristles may be connected tothe bristle support or brush body using any conventional joiningtechnique.

A further embodiment of the invention provides that the injection moldconsists of at least two groups of molding plates comprising clampingmeans of which the first group comprises part of the molding channelincluding the end and the further groups comprise the remaining part ofthe molding channel, wherein the first group can be removed from thesecond group and the subsequent groups can be removed from each other,in temporal sequence. The injection process is divided into a number ofinjection molding cycles corresponding to the number of groups suchthat, in the closed initial position of the injection mold, the moltenpolymer mass is injected in a first injection cycle into the completemolding channel, whereupon the first group can be removed from thefurther groups thereby carrying along the blank via the clamping means,with the withdrawal path being shorter than the length of the blank.Subsequently, in a second injection molding cycle, more molten polymermass is injected into the released longitudinal section of the moldingchannel of the further groups and the steps injection/removal arerepeated until the second to last group is removed from the last groupto produce bristles of a length greater than the length of the moldingchannel. The bristle is produced in sections, which permits productionof bristles of greater lengths.

In this embodiment of the device, a different molten polymer mass can beinjected in each injection cycle to produce a bristle which has severalcomponents along the bristle length, wherein the polymers used in eachstep can be matched to the requirements of the bristle and connection tothe bristle support thereby producing a bristle with several regions.The removal motions of the individual groups can be matched, in shorttime intervals, to the injection molding cycle, wherein the blank issufficiently cooled that it is removed from the remaining molding platesduring the withdrawal motion. The individual regions are preferablybonded together but may also be connected in a positive or non-positivemanner through corresponding profiling of the end of the last injectedpartial length.

The molding plate comprising the bristle end and the mold contour at theend of the molding channel can preferably be replaced with a moldingplate having a different mold contour for producing bristles with endsof different shapes. This molding plate should only have smooth contoursto permit faultless removal from the mold of the bristle end, which isimportant for the respective use.

In this fashion, the end contour of the bristles can be varied forotherwise constant geometry of the bristles, e.g. have pointed orvariably rounded ends or even to produce bristles with forked-ends (twotips or the like). This molding plate may have longitudinal moldingchannel sections of different depths to form a contoured envelopesurface for the bristle ends of a bristle stock.

A mold cavity, which connects two or more molding channels, ispreferably disposed between the supply channel and the molding channelsof the injection mold for forming a connection among the bristles whichcan optionally also connect all bristles. It can serve either as anauxiliary means for further handling of the entire bristle stock or asan auxiliary means for completing the bristle stock with a brush body.

The mold cavity can also be designed to produce a brush or paintbrushbody or part thereof.

In particular, the mold cavity can thereby be formed from differentpolymers for producing a brush or paintbrush body or part thereof in amultiple component design.

BRIEF DESCRIPTION OF THE DRAWING

The invention is described below with reference to embodiments shown inthe drawing.

FIG. 1 shows a schematic view of a bristle defining the bristle regionsand sections;

FIG. 2A shows a highly enlarged schematic view of a bristle inaccordance with a first embodiment;

FIG. 2B shows a top view of the bristle of FIG. 2A;

FIG. 3A shows a view of a bristle which is modified compared to FIG. 2A;

FIG. 3B shows the section IIIB-IIIB of FIG. 3A;

FIG. 3C shows the section IIIC-IIIC of FIG. 3A;

FIG. 4A shows a side view of a further embodiment of a bristle;

FIG. 4B shows the section IVB-IVB of FIG. 4A;

FIG. 4C shows the section IVC-IVC of FIG. 4A;

FIG. 5A shows a side view of a further embodiment of a bristle;

FIG. 5B shows the section VB-VB of FIG. 5A;

FIG. 5C shows the section VC-VC of FIG. 5A;

FIG. 6A shows a view of a further embodiment of the bristle;

FIG. 6B shows the section VIB-VIB of FIG. 6A;

FIG. 7A shows a view of a further embodiment of the bristle;

FIG. 7B shows the section VIIB-VIIB of FIG. 7A;

FIG. 8A shows a modification of the bristle of FIG. 7A;

FIG. 8B shows the section VIIIB-VIIIB of FIG. 8A;

FIG. 8C shows the section VIIIC-VIIIC of FIG. 8A;

FIG. 9 shows an alternative embodiment of the bristle;

FIG. 10 shows a bristle in particular for an application brush;

FIG. 11 shows a bristle with profiled tip section t;

FIG. 12 shows a further embodiment of the bristle;

FIG. 13 shows a bristle formed from parts of different materials;

FIG. 14 shows a further development of the bristle of FIG. 13;

FIG. 15A shows a side view of a bristle with cylindrical envelopingsurface;

FIG. 15B shows a top view of the bristle of FIG. 15A;

FIG. 16A shows the bristle of FIG. 15A with coated sections;

FIG. 16B shows a top view of the bristle of FIG. 16A;

FIG. 17A shows a side view of a bristle with inner hollow axial channel;

FIG. 17B shows a top view of the bristle of FIG. 17A;

FIG. 18A shows an alternative embodiment of a bristle with an innerhollow channel;

FIG. 18B shows a top view of the bristle of FIG. 18A;

FIG. 19A shows a modification of the bristle of FIG. 18A;

FIG. 19B shows a top view of the bristle of FIG. 19A;

FIG. 20A shows a bristle with axial fingers in the tip section;

FIG. 20B shows a top view of the bristle of FIG. 20A;

FIG. 21A shows a side view of the free end of a bristle with an axialprofiled element;

FIG. 21B shows a top view of the bristle of FIG. 21A;

FIG. 21C shows a top view corresponding to FIG. 21B with a firstalternative profiled element;

FIG. 21D show a top view corresponding to FIG. 21B with a secondalternative profiled elements;

FIG. 21E show a top view corresponding to FIG. 21B with a thirdalternative profiled elements;

FIG. 21F show a top view corresponding to FIG. 21B with a fourthalternative profiled elements;

FIG. 21G show a top view corresponding to FIG. 21B with a fifthalternative profiled elements;

FIG. 21H show a top view corresponding to FIG. 21B with a sixthalternative profiled elements;

FIG. 21I show a top view corresponding to FIG. 21B with a seventhalternative profiled elements;

FIG. 21J show a top view corresponding to FIG. 21B with a eighthalternative profiled elements;

FIG. 21K show a top view corresponding to FIG. 21B with a ninthalternative profiled elements;

FIG. 21L show a top view corresponding to FIG. 21B with a tenthalternative profiled elements;

FIG. 21M show a top view corresponding to FIG. 21B with a eleventhalternative profiled elements;

FIG. 22A shows a view of a further embodiment of the bristle;

FIG. 22B shows a view of the bristle of FIG. 22A;

FIG. 23A shows a view of a further embodiment of the bristle,

FIG. 23B shows a top view of the bristle of FIG. 23A;

FIG. 24A shows a view of a further embodiment of the bristle;

FIG. 24B shows a top view of the bristle of FIG. 24A;

FIG. 25A shows a view of a further embodiment of the bristle;

FIG. 25B shows a top view of the bristle of FIG. 25A;

FIG. 26 shows a longitudinal section through a bristle according to analternative embodiment;

FIG. 27A shows a schematic view of a conical bristle on a scale 2:1 withdimensioning;

FIG. 27B shows a schematic view of a conical bristle on a scale 5:1 withdimensioning;

FIG. 28 shows a comparative schematic view of the speed profiles in anextrusion nozzle and in a mold channel;

FIG. 29 shows a schematic longitudinal section through an embodiment ofan injection mold in a first operational phases;

FIG. 30 shows a schematic longitudinal section through an embodiment ofan injection mold in a second operational phases;

FIG. 31 shows a schematic longitudinal section through an embodiment ofan injection mold in a third operational phases;

FIG. 32 shows a schematic longitudinal section through an embodiment ofan injection mold in a fourth operational phases;

FIG. 33 shows a schematic longitudinal section through a furtherembodiment with reference to the injection mold;

FIG. 34 shows an enlarged detail of the injection mold according to FIG.33 in the region of an external mold channel;

FIG. 35 shows a schematic longitudinal section through a modifiedembodiment of an injection mold in a first operational phases;

FIG. 36 shows a schematic longitudinal section through a modifiedembodiment of an injection mold in a second operational phases;

FIG. 37 shows a schematic longitudinal section through a modifiedembodiment of an injection mold in a third operational phases;

FIG. 38 shows a schematic longitudinal section through a modifiedembodiment of an injection mold in a fourth operational phases;

FIG. 39 shows a schematic longitudinal section through a modifiedembodiment of an injection mold in a fifth operational phases;

FIG. 40 shows a schematic longitudinal section through a furtherembodiment of the injection mold in a first operational phases;

FIG. 41 shows a schematic longitudinal section through a furtherembodiment of the injection mold in a second operational phases;

FIG. 42 shows a schematic longitudinal section through a furtherembodiment of the injection mold in a third operational phases;

FIG. 43 shows a longitudinal section through the injection moldcorresponding to FIGS. 40 through 42 with a supplementary mold;

FIG. 44 shows a longitudinal section through an injection mold in afurther modified embodiment in a first operational phases;

FIG. 45 shows a longitudinal section through an injection mold in afurther modified embodiment in a second operational phases;

FIG. 46 shows a longitudinal section corresponding to FIG. 44 with acontoured displacement plate;

FIG. 47 shows a longitudinal section corresponding to FIG. 45 with acontoured displacement plate;

FIG. 48 shows a longitudinal section corresponding to FIG. 44 withanother form of injection molding;

FIG. 49 shows a longitudinal section corresponding to FIG. 45 withanother form of injection molding;

FIG. 50 shows a schematic longitudinal section through an injection moldfor producing bristles of different lengths; and

FIG. 51 shows a schematic section through an injection mold forproducing bristles with split bristle ends.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 2A and 2B show one individual bristle 100 which can be used inparticular for hygiene brushes, e.g. toothbrushes, cleaning brushes inthe medical field or in hospitals or also as cleaning or applicationbrushes in the food industry. The root region a of the bristle 100 has atrumpet-like downward facing widening with concave rounded flanksthereby providing good mounting to a surface 102 of a brush body. Alongits free length L, the bristle 100 has a conically tapering envelopingsurface wherein the shaft region S has a circular cross-section with acontinuous, smooth depression-free jacket along its entire length. Aprofiling 101 is formed in the flexing region F, with the bristle 100having a crossed cross-section in this location (see FIG. 2B) to formfour axial ribs 103 which are distributed about the circumference, whichare rounded at their outer sides, and which extend up to the free end ofthe bristle 100. A smooth, continuous transition is provided between theouter side of the ribs 103 and the surface of the shaft region S. Thebristle 100 is rounded in the region of its free end.

FIGS. 3A, 3B and 3C show a further development of the bristle of FIG. 2Awhich differs therefrom only in that the ribs 103 forming the profiling101 are connected to a central section 104 having a peripherally smooth,continuous and depression-free surface to form two axially separatedprofilings 101 of the above mentioned type between which the centralsection 104 having a smooth depression-free jacket is disposed. Thesurface of the ribs 103 merges smoothly and continuously into thedepression-free jacket of the section 104 or shaft region.

The upper region of the active and flexing section and the tip sectionof the bristle 100 of FIGS. 4A, 4B and 4C have the above-mentionedprofiling 101 with crossed cross-section (FIG. 4B). A section 104 withsmooth, depression-free envelope is disposed below the profiling 101. Afurther profiling 105 is formed below this section 104, which comprisesa plurality of axially extending grooves 106 which are closely disposednext to each other about the periphery of the bristle. A sharp edge 107is formed between two neighboring grooves 106 (FIG. 4C).

The bristle 100 of FIGS. 5A, 5B and 5C differs from the bristle of FIG.4A in that the profiling 108 is an arrangement of several horizontalgrooves 109 which extend about the periphery of the bristle, each ofwhich having a V-shaped cross-section, wherein a circumferential, sharpradial edge 110 is formed between each of the stacked grooves 109.

FIGS. 6A and 6B show a modification of the bristle according to FIG. 2Aand differ from this figure in that the profiling 101 has a triangularcross-section instead of a crossed cross-section (see also FIG. 6B) tocreate three sharp axial edges 111 which are distributed about thecircumference of the bristle. The triangular cross-section extends up tothe free end of the bristle 100.

FIGS. 7A and 7B show a further alternative of the cross-sectional designof the profiling. In accordance with this embodiment, the profiledregion 101 of the bristle 100 has a cross-section formed by threeaxially upwardly protruding ribs 103 wherein each rib has thecross-sectional shape of a segment of a circle and a gap 112 is formedbetween the ribs 103 such that the ribs 103 are only connected to eachother in the base region.

FIGS. 8A, 8B and 8C show a further development of the embodiment of FIG.7A which differs therefrom only in that the ribs 103 have an externalrecess 113 of concave cross-section in an upper partial region of theiraxial length which extends in the longitudinal direction of the bristle100 up to the upper free end of the bristle 100.

In all of the above-mentioned embodiments, the bristle has across-section, which tapers continuously towards the tip. Thecross-sectional dimensions of the bristle in the region of its freelength do not exceed the cross-sectional dimensions of the lower portionof the shaft base section b where the bristle merges into the underlyingroot region a. FIG. 9 shows one embodiment in which the shaft basesection b has a cylindrical shape and the sections disposed above, i.e.the shaft section c of the active and flexing section d and the tipsection t, taper towards the top. The entire active and flexing sectiond has a profiling 108 which is formed by a plurality of horizontalgrooves 109 extending around the bristle 100 with intermediate sharpcirculating edges 110. FIG. 9 shows that the bristle has a circularcross-section in the region of the active and flexing section d and itsupper tip section t has a square cross-section to form four sharp axialedges 111.

The bristle 100 of FIG. 10 has a circular cross-section with smoothdepression-free envelope throughout its overall shaft region S and itsactive and flexing section d, wherein the shaft section c and the activeand flexing section d are conical. Three contiguous fingers 114 whichextend axially in an upward direction form the tip section t. In thisembodiment, three fingers are provided which are disposed at the cornersof a substantially equilateral triangle.

The bristle 100 of FIG. 11 differs from the bristle of FIG. 10 withrespect to the design of the tip section t. Instead of the fingers 114,the tip section t now has a profiling 115 in the form of a square orrhombic cross-section to form four sharp axial edges 111. The bristlehas no profile outside of the tip section t and has a smoothdepression-free jacket.

While in the embodiment of FIG. 11, the entire tip section t has aprofiling 115, FIG. 12 shows a design having an upwardly facing recess115 a with concave cross-section which is additionally formed on thefree end of the bristle and whose circumferential edge serves as anadditional profiling.

FIG. 13 shows a bristle 100 which is formed of axially sequentialsections or parts 100 a and 100 b of different materials. A firstsection 100 a thereby forms the shaft section s, i.e. the shaft basesection b and the shaft section c and consists of a foamed material,which may have a certain surface roughness. A second section 100 b isprovided thereabove, which forms the active, and flexing section d andthe tip section c and which consists of non-foamed material. The tipsection t and the upper region of the active and flexing section d has aprofiling 101 in the form of a crossed cross-section with four ribs 103distributed about the periphery of the bristles.

FIG. 14 shows a further development of the bristle of FIG. 13 having athird section 100 c which forms the active and flexing section d, whichconsists of a material filled with an additive or substance forantimicrobial action, and which may also have a certain surfaceroughness.

While in the embodiments described up to now, the bristle has a conicitywhich tapers towards its free end at least along partial regions of itslength, FIGS. 15A and 15B show a bristle 100 comprising a cylindricalenveloping surface. A profiling 101 corresponding to the bristle of FIG.2A is formed in the region of the tip section and at least in the upperregion of the active and flexing section. In accordance with a furtherdevelopment as shown in FIGS. 16A and 16B, the profiling 101 has anexternal coating 116 which completely surrounds the outer surface of thebristle 100 in the region of the profiling 101.

FIGS. 17A and 17B show a further development of the bristle of FIG. 2Aand differ therefrom only in that the bristle 100 has a hollow axialchannel 117 travelling in the longitudinal direction which starts at thelower end of the root region and extends approximately to half theheight of the bristle. The hollow axial channel 117 may be filled withactive substances, e.g. sodium fluoride, xylite or other organic orinorganic materials and can gradually release them to the surface of thebristle during use. While the cavity only extends to the lower end ofthe structure 101 in FIG. 17A, FIGS. 18A and 18B show a bristle 100 withcylindrical enveloping surface which has a hollow axial channel 117which extends approximately through the entire length of the bristle toshortly below the free end. The front end of the hollow channel in thevicinity of the free end of the bristle has a thin sealing membrane 117a made from the bristle material itself and through which the activesubstance located in the hollow channel 117 can be released.

FIGS. 19A and 19B show a further development of the bristle of FIG. 18A,wherein the hollow channel 117 extends through the entire bristle andopens in the tip section at its free end.

The bristle 100 shown in FIGS. 20A and 20B is uniformly cylindrical withthe exception of its tip section. The tip section is formed by aplurality of integral fingers 114 extending axially and upwardly.Instead of the plurality of parallel integral fingers 114, the tipsection may be formed by a profiled element 118 having one or morecomponents (shown in FIGS. 21A through 21M). In the design of FIGS. 21Aand 21B, the profiled element 118 is formed by a vertical, substantiallyrectangular wall with rounded ends. Alternatively, in accordance withFIG. 21C, two mutually crossing walls which are correspondingly disposedperpendicular to each other are provided thereby forming a crossedsection. FIG. 21D shows the profiled element as three axially freelyprotruding integral pins which are mounted at their lower ends and whichhave circular cross-sections. FIG. 21E shows a profiled element in theform of three mutually crossing walls arranged to form a star-shapedcross-section.

Instead of providing a substantially rectilinear wall in accordance withFIG. 21A, FIG. 21F shows a curved, thin wall with a meandering ordouble-S-shaped cross-section. The active and flexing section disposedbelow the profiled element 118 does not have the previously describedcircular cross-section, rather an oval cross-section. FIG. 21G shows adesign corresponding to FIG. 21F with the difference being that theactive and flexing section bearing the profiled element 118 now has arectangular cross-section with rounded edges.

In accordance with FIG. 21H, the profiled element has a triangularcross-section with three sharp outer edges. The profiled element inaccordance with FIG. 21I is created in a solid cross-section in whichtwo axial slots, disposed perpendicularly with respect to each other,are formed to generate four independent vertical pins, each having acircular segment cross-section.

In accordance with FIG. 21J, the tip section has four walls distributedabout the periphery and formed with a radially outwardly concave shapewhich have effective edges in each of their end regions.

FIG. 21K shows a profiled element 118 with a star-shaped cross-sectioni.e. an inner core which has axial grooves on its outside withintermediate outwardly facing sharp edges.

FIG. 21L shows an active and flexing section with oval cross-section onwhich three short curved walls are disposed whose convex surfaces aredirected radially outwardly. Two of the walls are disposed next to oneanother and the third wall is laterally offset thereto. FIG. 21M shows amodification of this embodiment, wherein the active and flexing sectionhas a rectangular cross-section with rounded edges and the walls formingthe profiled elements 118 have an L-shape and are radially outwardlyangled.

FIGS. 22A and 22B show a modification of the bristle in accordance withFIG. 2A which differs therefrom in that the profiling 101 is formed notonly in the tip region and in the active and flexing section but also inthe upper region of the shaft section. The shaft base section and thebordering lower region of the shaft section are also provided with acontinuous, smooth, and depression-free jacket.

In the embodiments mentioned above, the transition between theunprofiled jacket and the profiling was always in a plane extendingsubstantially perpendicular to the longitudinal axis of the bristle as aresult of which the bristle has similar usage properties independent ofits peripheral orientation. FIGS. 23A and 23B show a bristle with whichthe transition between the lower unprofiled jacket and the upperprofiling 108 formed by a plurality of horizontal circulating groovesabove which a further profiling 101 with crossed cross-section and axialribs 103 is disposed, is in a plane E extending at an angle with respectto the longitudinal axis of the bristle. In the embodiment shown, theplane E has an inclination of approximately 45°. The bristle thereforehas a profiling along a larger part of its length at the left-hand sideof FIG. 23A than on the right-hand side of FIG. 23A and the brushing andcleaning properties of the bristle consequently depend on theorientation with which they are fixed to the bristle support.

FIGS. 24A and 24B show a modification of the bristle in accordance withFIG. 13. The bristle 100 also consists of several parts 100 a and 100 bmade from different materials. The surface of the lower part 100 a maybe roughened. The connection between the two parts 100 a and 100 b isobtained through a funnel-shaped contacting surface 100′, which permitsappropriate connection between the parts 100 a and 100 b even forrelatively small bristle sizes. The profiling 101 is formed in the tipsection of the bristle 100 by a crossed cross-section with four axiallyextending ribs 103.

FIGS. 25A and 25B show a bristle corresponding to FIG. 2A having anadditional external cover 119 in the lower region of the shaft section,shaft base section and root region which can reinforce and stabilize thebristle and/or provide visual indication of certain bristle properties.

In accordance with FIG. 26, the entire bristle is provided with a cover119 wherein the tip section has several axially upwardly protrudingfingers 120 which penetrate through the cover 119.

A possible production method of a corresponding inventive bristle isexplained in detail below wherein the illustrations show a bristlewithout surface profile for reasons of simplification.

The above mentioned operating parameters for injection pressure and theachievable high core speeds with large shearing effect through wallfriction produce thin bristles of adjustable length using injectionmolding, which has not been possible up to now, not even with extrusionof endless monofilaments, wherein even weak conicity of bristles of suchendless monofilaments can be realized only through considerabletechnical effort (interval withdrawal). FIGS. 27A and 27B show twoembodiments. FIG. 27A shows (scale 2:1) a bristle having a diameter of0.77 mm in the root region and of 0.2 mm at the bristle end, and with anaverage diameter of 0.49 mm at half-length. With an extremely weakconicity angle of 0.27°, which corresponds to the mold slope of thebristle-molding channel, bristles of a length of 60 mm or more can beinjection-molded as are required e.g. for high-quality paint brushes orthe like. They have an average diameter at half bristle length ofapproximately 0.5 mm. FIG. 27B shows (scale 5:1) a bristle of a diameterof 0.35 mm in the root region and of 0.25 mm at the bristle end with abristle length of 10.5 mm and the same conical angle (mold slope). Theaverage diameter is 0.3 mm. Bristles of this type are suited e.g. fortoothbrushes. Due to the slender geometry of such bristles, they can bedensely arranged without producing excessive separation in the region ofthe bristle ends—in contrast to conventional injection-molded bristles.

FIG. 28 shows the superiority in terms of technical properties andapplications, of the bristle produced according to the inventioncompared to a bristle produced by extrusion.

During extrusion spinning of a monofilament for producing a bristle ofan average diameter of 0.3 mm, the spinning nozzle has an outletdiameter of 0.9 mm (outer vertical lines in FIG. 28). The molten polymermass has a maximum flow speed (core speed) inside the nozzle oftypically approximately 300 mm/s, which is determined by the extrusionpressure and the withdrawal speed of the monofilament. The monofilament,which leaves the nozzle, is drawn along a short path, by means of thewithdrawal forces, to a diameter of between 0.9 and 0.3 mm and cooleddirectly thereafter to fix the molecular structure. During subsequentdrawing, the monofilament is given its final diameter of 0.3 mm with adiameter tolerance of approximately ±10%. The speed profile isdesignated as e (extrusion) in FIG. 28.

In the inventive injection molding, the bristle-molding channel has anaverage diameter of 0.3 mm (the two inner vertical boundary lines inFIG. 28). An injection pressure in the region of 2000 bar (2·10⁵ kPa)produces a core speed of approximately 1000 mm/s in the channel. Thespeed profile is designated as i (injection). The shearing effect in theflow, in particular in the region close to the wall is relevant for theintrinsic strength of the thermoplastic polymer, which is determined bythe shearing rate (shearing moment) γ. The shearing rate γ across theradius r of the flow channel depends on the derivative of the speedprofile with respect to the radius r

${\gamma(r)} = {{{{\mathbb{d}{v(r)}}/{\mathbb{d}r}}} = {\frac{2v_{\max}}{R^{2}} \circ r}}$which is inversely proportional to the square of the effective diameterof the flow channel. The shearing rate is linearly proportional to themaximum flow speed (core speed). In the above-described example shearingrates for the injected bristle are produced which exceed the statedextrusion flow by at least a factor of 10.

The broken lines in FIG. 28 illustrate the shearing rates withoutscaling for extrusion (e₁) and for injection molding (i₁). They haverespective maxima at the walls of the nozzle of the bristle-moldingchannel.

FIGS. 29 to 32 schematically show an embodiment of an injection mold indifferent operational phases which is particularly suited for injectionmolding of the bristles according to the inventive method. The scale ishighly enlarged to show the details more clearly.

The injection mold 1 has several long parallel molding channels 2 whichare joined to an injection molding means via a supply channel 3. Theinjection molding means is designed to produce injection pressures inthe region of 500 bar (0.5·10⁵ kPa), preferably ≧2000 bar (2·10⁵ kPa).The exact magnitude of the injection pressure is set in dependence onthe cross-sectional shape of the molding channel 2 along its length andin dependence on the length itself such that a specific pressure >300bar (0.3·10⁵ kPa) occurs in the molding channel.

The injection mold consists of a plurality of layered molding plates 4of substantially identical thicknesses, of a molding plate 5 on theinjection side, and a molding plate 6 forming the bristle ends. Eachmolding plate 4, 5 and 6 generates one longitudinal section of themolding channel 2, which is preferably produced by bore holes.

The molding plate 5 has openings 7 on the injection side which narrowtowards the molding channel 2 to produce e.g. the extension flow andform the root region a of the bristle. The subsequent longitudinalsections of the molding channel in the molding plates 4 have acylindrical or slightly conical cross-sectional shape along their lengthwhile the molding plate 6 forming the bristle ends has blind holes 8which are dome-shaped in the embodiment shown.

During injection molding, the molten polymer mass enters into thenarrowing openings 7 of the molding plate 5 via the supply channel 3and, due to the high core speed, fills the entire molding channel up tothe plate 6 forming the ends. The molten polymer mass has asubstantially unordered, balled molecular structure in the supplychannel 3 which is transformed into a longitudinal molecular structurein the opening 7 on the injection side and subsequent molding channel 2due to the strong shear flow.

The molding plates 4, 5 and 6 can be moved perpendicular to the plane ofthe plate to release the injection-molded bristles when they haveachieved sufficient shape stability. The injection molding tool 1 ispreferably cooled such that the wall of the molding channels 2 remainsrelatively cold, thereby supporting the formation of crystals in themolten polymer mass.

To release the bristles from the mold, the molding plate 6 is initiallyremoved (FIG. 30). Only very small adhesive forces must be overcomethereby ensuring that the bristle ends, which are particularly importantfor later use of a brush or a paintbrush, maintain their shapes. Themolding plates 4 are subsequently removed individually or in groups(FIG. 31) until the ends 10 of the bristles 9 are released along most oftheir length. During these releasing steps, the bristles are retained bymeans of the molding plate 5 on the injection side and this moldingplate 5 is also subsequently removed to expose all bristles 9 with theirslightly thickened root region 11 (FIG. 32). The molten polymer mass inthe supply channel on the injection side also effects a connection 12among all bristles 9 and the overall blank can be removed and finishedinto a brush, a paint brush or the like, wherein the connection iseither integrated into the structure or only serves as auxiliary meansfor handling the bristles and is separated off before connecting thebristles to a brush body or the like.

Optimum venting of the molding channels must be provided duringinjection molding to facilitate the desired high core speed. FIG. 33shows an embodiment thereof. Venting occurs via narrow gaps 13 betweenthe molding plates 4, 5 and 6 so that the air is removed along theentire length of the molding channels 2 as the front advances. Insteadof narrow gaps 13, it is also possible to roughen the mutually facingsurfaces of the molding plates 4, 5 and 6, to obtain overall ventingcross-sections of sufficient size. The venting cross-sections havewidenings 14 towards the outside to permit rapid escape of theexhausting air.

The molding channels 2 may taper along their entire length with a moldslope <1.0°, wherein the tapering is not dictated by release from themold but rather by the desired bristle shape and its bending behavior.The cross-sectional shape of the molding channels 2 must not becontinuously conical (see the enlarged scale of FIG. 34 illustrating theventing geometry). The upper molding plate 4 in the drawing indicates acylindrical longitudinal section 15 and the lower molding plate 4 acylindrical longitudinal section 16 for the molding channel 2. Thecross-section of the two molding plates 4 tapers from the longitudinalsection 15 to the longitudinal section 16 of the molding channel 2 by afew μm to produce a weak step at this point. At this step region,venting takes place via the gap 13 between the two molding plates, whichmap into a widening 14. During release from the mold, these unnoticeablesteps are not visible and produce slight conicity along the entirelength of the bristle. The longitudinal sections 15, 16 in theindividual molding plates 4 can be produced through simple drilling.Alternatively, the longitudinal sections of the individual moldingplates can have identical diameters to produce a cylindrical bristle.More distinct diameter changes produce stepped bristles.

Conical bristles are technically advantageous for injection molding andfor removal from the mold. The smallest cross-section at the bristle endcools more rapidly than the subsequent regions of the bristle towardsthe root region and the step-by-step release from the bristle end to thebristle root follows the temperature gradient in the bristle.

The molding plates 4 have a thickness of a few millimeters. It maycorrespond approximately to three to fifteen times the diameter of themolding channel 2 so that extremely precise drilling of the longitudinalsections in the individual molding plates is possible. Since they arekept adjacent to one another under the closing pressure of theinjection-molding machine, even these thin molding plates maintain theirdimensions and shape, despite the high injection pressure. The lowthickness also ensures good thermal dissipation, since the moldingplates are evenly insulated by the venting gaps. They are easy to coolfor the same reason, e.g. using external coolants, which can beparticularly effective when the mold is closed, and also during the timebetween opening and renewed closing. Effective cooling already occursvia the surrounding air due to exposure of the molding plates and inconsequence of their small thickness. Alternatively, the cooling meansmay be integrated in or between the molding plates. Finally, the minimalloading under injection pressure permits production of the moldingplates from materials having good thermal conductivity with lessstringent mechanical strength properties than steel or the like.

The influence of effective cooling on the molecular structure of thebristles has already been discussed above.

FIG. 35 also schematically shows an injection mold 1 which consists oflayered molding plates 4, wherein the molding plate on the injectionside does not have widened cross-sections. In contrast to theabove-described embodiments, the molding plates 4 are divided into twogroups 17, 18 (see FIG. 36) wherein each group comprises at least onemolding plate which can be transversely displaced (indicated in FIGS. 36to 39 with double arrows 19, 20.)

The transversely displaceable molding plates cooperate with theneighboring molding plates to clamp the blanks 21, which, in thisembodiment, only form one portion (longitudinal section) of the finalbristle. The blank 21 is injected from a thermoplastic polymer withinjection parameters matched to this longitudinal section of thefinished bristle. After the injection cycle, at least one displaceableplate of the group 18 of molding plates 4 (FIG. 36) is brought into aclamping position and the blanks 21 are carried along when the group 18is removed to be thereby partially released from the molding plates 4 ofthe group 17 on the injection side and free a predetermined longitudinalsection 22 of the molding channels in the molding plates 4 of the group17. At the end of the blank 21, profilings may be optionally formed asindicated in the drawing. After withdrawal of the molding plates 4 ofthe group 18, the displaceable molding plate in the group 17 is broughtinto the clamping position and the exposed longitudinal sections 22 aresubsequently filled with a molten polymer mass, which consists ofanother polymer or a polymer with other additives. The longitudinalsections 23 of the bristle which are formed thereby connect to theblanks 21 through material bonding and/or positive locking.Subsequently, the displaceable forming plate in group 17 is returned toits initial position and the blanks 21 with molded-on longitudinalsections 23 are again partially withdrawn from the molding channels ofthe group 17 when the clamping means is closed to expose longitudinalsections 24 in the molding channels. In a further injection moldingcycle, the longitudinal sections 24 are filled with a further moltenpolymer mass with optionally further differentiated properties tofinally obtain bristles 27 having three regions (sections 21, 23 and 25)for different mechanical strength properties and/or different usageproperties along the bristle length. In particular, the region 21, whichencloses the bristle end, can serve as wear display to show the degreeof wear of the bristle. Final release of the bristles from the mold iscarried out as described above.

FIGS. 40 to 43 also show an injection mold 1 (FIG. 40) which consists oftwo groups 17, 18 of molding plates 4 each of which has at least onetransversely displaceable molding plate to form a clamping means. Incontrast to the above-described embodiment, the molding plate 5 on theinjection side has widenings, which taper towards the molding channel.The molding plate 6 forming the bristle ends has blind holes 28, 29 and30 of different depths with dome-shaped hole bottoms such that aplurality of bristles of different lengths can be produced whose endslie on a curved envelope surface.

In the embodiment of FIGS. 40 to 43, bristles are injected sequentiallywith two different regions 31, 32 wherein the region 31 has an extendedbristle root 33. The multiple-section bristles 34 (FIG. 41) injected inthis fashion are subsequently removed from the mold at their ends byremoving the molding plate 6 forming the bristle ends and—optionallywith delay—removing the molding plates 4 of the group 18 (FIG. 41).Subsequently, at least one transversely displaceable molding plate inthe group 18 is brought into a clamping position and the entire group18, optionally together with the terminal molding plate 6, is displacedin the opposite direction so that the part of the region 31 of thebristles 34 including the root region 33 project past the molding plate5 at the injection side. Subsequently, the injection mold 1 (FIG. 42) isconnected to a further injection mold 35 with a mold cavity 36 intowhich a molten polymer mass is injected with which the root regions 23and the longitudinal sections of the regions 31 which project into thecavity 36 are injected. The mold cavity 36 may be formed so that itdefines an intermediate support for the bristles or a complete brushbody in which the bristle ends are embedded without gaps so that theycannot be pulled out.

In a modification of this embodiment, the molding channels 2 of theinjection mold 1 of FIG. 40 can also be completely filled with onesingle molten polymer mass and, as shown in FIGS. 41 and 42, their rootregions can be exposed together with the adjacent longitudinal sectionsfor injection with the support-forming molten polymer mass (FIG. 43).

In a further modification, the bristles which are injected according toFIGS. 40 to 42 and released at their mounting-side ends can becompletely released from the mold through removing the molding plate 6forming the ends and the major part of the subsequent molding plates 4while being held by a few, at least three, molding plates, e.g. theinjection-side molding plate 5 and the two subsequent molding plates oneof which can be transversely displaced to form a clamping means. Thesemolding plates, which serve as a transport holder, can be transportedtogether with the bristles into another injection molding station inwhich they are brought into connection with the injection mold 35 whilesimultaneously providing a new set of molding plates with injection-sidemolding plate 5 to complete the injection mold 1. This transport holdercan move the bristles into the second injection molding station and alsocontinue transport into other processing stations.

FIGS. 44 and 45 show part of an injection mold 1 with molding plates 4and 5 after production of the bristles and removal of at least the lastmolding plate 6 (not shown). Replacing the latter, a flat thrust plate39 is moved in front of the released ends with which the bristles 38 aredisplaced in the molding channels of the remaining molding plates untiltheir root region 37, and optionally an adjoining longitudinal section,project past the injection-side molding plate 5 or into the mold cavity36 of the further injection mold 35 and are injected with a moltenpolymer mass to form a bristle support or a brush body.

FIGS. 46 and 47 show an embodiment with which, after production of thebristles 38 as described with reference to FIGS. 44 and 45, instead ofthe flat thrust plate 39, a thrust plate 40, which has cam-likeprojections 41 and 42 of different heights, is moved in front of thereleased bristle ends. When the thrust plate 40 has been moved towardsthe molding plates 4, the bristles are displaced along the thrust pathto different depths within the molding channels so that their rootregion 37 projects into the mold cavity 36 of the injection mold 35 todifferent depths and the bristle ends lie on a curved envelope surfaceafter injection and removal of the thrust plate 40 and molding plates 4and 5.

FIGS. 48 and 49 show an embodiment which differs from that of FIGS. 44and 45 only in that the bristles 38 are interconnected in the region ofthe injection-side molding plate 5 via a connection 43 in the form ofbars, grids or the like and project with the connection 43 and thesubsequent longitudinal sections of the bristles 38 into the cavity 36of the injection mold 35 after displacement via the thrust plate 39.

A smaller group of molding plates 4, preferably including theinjection-side molding plate 5 and with at least one molding plate 4which can be transversely displaced to act as clamping means, may serveas transport holder for transferring the bristles into further injectionmolding stations, processing stations or the like.

The layered structure of the injection mold from a plurality of moldingplates and the thereby possible sectional removal from the mold and theincrease in the modulus of elasticity and tensile strength obtained bythe inventive method parameters of injection pressure and flow speed inthe molding channel permit production of bristles whose central axis isnot in the direction of release from the mold. FIGS. 50 and 51 showexamples thereof. FIG. 50 shows a part of an injection mold withslanting molding channels 44, 45 that are inclined towards each other inthis embodiment. In addition to or alternatively, the injection mold 1may have wavy, curved molding channels 46 or molding channels 47 withseveral bends so that correspondingly formed bristles are produced whichcan be injected in a composite action via a connection 48. For releasefrom the mold, the molding plates 4 and 6 are removed, starting withmolding plate 6, and the bristles are released in sections without beingdeformed due to their high bending elasticity and the small releaselength.

The bristles may be fabricated into a brush after separation of theconnection, individually or in groups or together with the connection 48through injection around it or through other conventional thermal ormechanical connection methods.

In the embodiment of FIG. 51, the injection mold 1 has layered moldingplates 4 and two end molding plates 49, 50 that form distinctivelybranched bristle ends. The injection-molded bristles 51 each havefinger-like bristle ends 52 which can be easily removed from the molddue to the thin molding plates and the increased stability of thebristles.

The molding plates 6 or 49, 50 which form the bristle ends can be madefrom a sintered metal, in particular, for distinctly branched bristleends which also provides additional venting in this region toeffectively prevent trapping of air. The molding plates 4 can, ofcourse, also be made from such sintered metals to support venting of themolding channels. Micro-roughness which exists e.g. in sintered metalsor which can be produced through surface treatment of the moldingchannel produce corresponding roughness in the micro region on thesurface of the finished bristle which have a moisture repellant “Lotus”effect during use of the bristle.

1. A bristle for mounting in or to a bristle support, in particular fora cleaning brush, a toothbrush, or an application brush, the bristlecomprising: a lower root region, said root region for mounting in or tothe bristle support or for forming a part of the bristle support; alower shaft base section bordering said root region; a shaft sectiondisposed adjacent to and above said lower shaft base section, said lowershaft base section and said shaft section forming a shaft region; alower active flexing section bordering above said shaft region; a tipsection disposed above and adjacent to said lower active flexing sectionand defining a free end of the bristle, said lower active flexingsection and said tip section constituting a flexing region, said flexingregion and said shaft region constituting a free length of the bristlelying outside of the bristle support and being disposed above said rootregion, wherein the bristle has a continuous, depression free jacket insaid shaft base section and in said shaft section, and at least portionsof a jacket in said flexing region have a profiling defining elevationsand/or depressions disposed within a peripheral surface of the bristle;wherein said profiling comprises at least one groove which extends aboutthe bristle, and wherein said shaft region comprises 15% to 85% of saidfree length of the bristle; and wherein at least section of said freelength of an outer surface of the bristle have a conical or a truncatedconical envelope.
 2. The bristle of claim 1, wherein said profiling isformed in an upper region of said active flexing section and/or in saidtip section.
 3. The bristle of claim 1, wherein only said tip section isprovided with said profiling.
 4. The bristle of claim 1, wherein across-section of the bristle in said shaft base section and/or in saidshaft section and/or in said active flexing section is circular, oval orpolygonal with rounded corners.
 5. The bristle of claim 1, wherein atleast sections of said free length of an outer surface of the bristlehave a straight cylindrical envelope.
 6. The bristle of claim 1, whereina conicity angle is smaller than 50 or smaller than
 10. 7. The bristleof claim 1, wherein at least sections of a bristle jacket have aroughness or a roughness in a micro range.
 8. The bristle of claim 1,wherein a geometrical cross-sectional shape of the bristle changes insaid tip region.
 9. The bristle of claim 1, wherein transitions betweenprofilings and/or between said profiling and said depression-free jacketare smooth and continuous.
 10. The bristle of claim 1, wherein a sectionwith a depression-free jacket is disposed between two axially separatedprofilings.
 11. The bristle of claim 1, wherein several grooves aredisposed one on top of an other.
 12. The bristle of claim 1, wherein asharp edge is formed between neighboring grooves.
 13. The bristle ofclaim 1, wherein the bristle has a crossed or star-shaped cross-sectionin a region of said profiling with several ribs extending in alongitudinal direction of the bristle which are distributed about abristle periphery.
 14. The bristle of claim 1, wherein the bristle hasone of a polygonal, a triangular, and a four-sided cross-section in aregion of said profiling.
 15. The bristle of claim 1, further comprisingregions in which two different profilings overlap one another.
 16. Thebristle of claim 1, wherein said tip section is formed by axiallyextending fingers.
 17. The bristle of claim 1, wherein said the bristlecomprises axially sequential parts of different materials.
 18. Thebristle of claim 17, wherein at least one of said parts is colored. 19.The bristle of claim 17, wherein at least one of said parts is designedas a wear indicator.
 20. The bristle of claim 1, wherein the bristle hasan inner hollow axial channel, starting from said root region.
 21. Thebristle of claim 20, wherein said hollow channel extends through anentire bristle to just below said free end.
 22. The bristle of claim 20,wherein said hollow channel extends through an entire bristle and opensinto said tip section.
 23. The bristle of claim 1, wherein saidprofiling has at least one axial profiled element, which forms said tipsection.
 24. The bristle of claim 1, wherein a transition between saidprofiling and an unprofiled jacket is in a plane, which extendssubstantially perpendicular to a longitudinal axis of the bristle. 25.The bristle of claim 1, wherein a transition between said profiling andan unprofiled jacket is in a plane, which extends at an angle withrespect to a longitudinal axis of the bristle.
 26. The bristle of claim1, wherein an entire bristle 15 provided with a cover.
 27. The bristleof claim 1, wherein said shaft base section has an axial length of ≦10mm or ≦1 mm.
 28. The bristle of claim 1, wherein said bristle hasstructural properties defined by casting or injection molding of thebristle.
 29. The bristle of claim 1, wherein said shaft region comprises35% to 65% of said free length of the bristle.
 30. A bristle formounting in or to a bristle support, in particular for a cleaning brush,a toothbrush, or an application brush, the bristle comprising: a lowerroot region, said root region for mounting in or to the bristle asupport or for forming a part of the bristle support; a lower shaft basesection bordering said root region; a shaft section disposed adjacent toand above said lower shaft base section, said lower shaft base sectionand said shaft section forming a shaft region; a lower active flexingsection bordering above said shaft region; a tip section disposed aboveand adjacent to said lower active flexing section and defining a freeend of the bristle, said lower active flexing section and said tipsection constituting a flexing region, said flexing region and saidshaft region constituting a free length of the bristle lying outside ofthe bristle support and being disposed above said root region, whereinthe bristle has a continuous, depression free jacket in said shaft basesection and in said shaft section, and at least portions of a jacket insaid flexing region have a profiling defining elevations and/ordepressions disposed within a peripheral surface of the bristle; whereinsaid profiling comprise at least one groove which extends about thebristle, and wherein said shaft region comprises 15% to 85% of said freelength of the bristle; and wherein said profiling has severallongitudinal grooves disposed next to each other about a circumferentialdirection of the bristle.
 31. A bristle for mounting in or to a bristlesupport, in particular for a cleaning brush, a toothbrush, or anapplication brush, the bristle comprising: a lower root region, saidroot region for mounting in or to the bristle support or for forming apart of the bristle support; a lower shaft base section bordering saidroot region; a shaft section disposed adjacent to and above said lowershaft base section, said lower shaft base section and said shaft sectionforming a shaft region; a lower active flexing section bordering abovesaid shaft region; a tip section disposed above and adjacent to saidlower active flexing section and defining a free end of the bristle,said lower active flexing section and said tip section constituting aflexing region, said flexing region and said shaft region constituting afree length of the bristle lying outside of the bristle support andbeing disposed above said root region, wherein the bristle has acontinuous, depression free jacket in said shaft base section and insaid shaft section, and at least portions of a jacket in said flexingregion have a profiling defining elevations and/or depressions disposedwithin a peripheral surface of the bristle; wherein said profilingcomprises at least one groove which extends about the bristle, andwherein said shaft region comprises 15%to 85% of said free length of thebristle; and wherein at least portions of the bristle are provided witha coating.
 32. The bristle of claim 31, wherein at least portions ofsaid profiling are provided with said coating.
 33. The bristle of claim31, wherein said coating is designed to indicate wear.
 34. A bristle formounting in or to a bristle support, in particular for a cleaning brush,a toothbrush, or an application brush, the bristle comprising: a lowerroot region, said root region for mounting in or to the bristle supportor for forming a part of the bristle support; a lower shaft base sectionbordering said root region; a shaft section disposed adjacent to andabove said lower shaft base section, said lower shaft base section andsaid shaft section forming a shaft region; a lower active flexingsection bordering above said shaft region; a tip section disposed aboveand adjacent to said lower active flexing section and defining a freeend of the bristle, said lower active flexing section and said tipsection constituting a flexing region, said flexing region and saidshaft region constituting a free length of the bristle lying outside ofthe bristle support and being disposed above said root region, whereinthe bristle has a continuous, depression free jacket in said shaft basesection and in said shaft section, and at least portions of a jacket insaid flexing region have a profiling defining elevations and/ordepressions disposed within a peripheral surface of the bristle; whereinsaid profiling comprises at least one groove which extends about thebristle, and wherein said shaft region comprises 15% to 85% of said freelength of the bristle; and wherein said root region and said shaft basesection are provided with a cover.
 35. The bristle of claim 34, whereinsaid cover is part of the bristle support.